This invention relates to an improved anode-fitting assembly for use in the cathodic protection of metal surfaces such as the internal wall of water heaters, water tanks, pipelines, gas lines, heat exchangers, and the like.
When metals, particularly iron, are exposed to air and water, they undergo corrosion. The corrosion reaction is slow in pure water, but rapid in solutions of electrolytes. The corrosion reaction can be explained as an electrochemical phenomenon. It appears that minute, primary electrical cells are set up when corrosion takes place. When iron is in contact with water containing electrolytes, iron ions immediately go into solution. From a somewhat oversimplifieid point of view, one may imagine that the attractive forces of the electrolyte molecules exceed the cohesive forces which hold the iron ions in their crystalline lattice. Every positive ion which goes into solution leaves one electron behind for each valence which the ion possesses. These electrons tend to collect at the less active portions of the ions (having a lower electrode potential) and combine with hydrogen ions to form hydrogen gas. Several methods of preventing or retarding corrosion have been proposed including alloying iron with certain other elements such as chromium or silicon and application of electrochemistry to produce cathodic protection.
This invention relates to electrochemical protection of iron and other metals through cathodic protection. The primary function of this invention is to provide a galvanic anode-fitting assembly adapted to be introduced into a water heater, pipeline, or the like. The anode element includes an electrode fabricated from a metal that is more active than the metal comprising the water heater, pipeline or the like. The more active metal is electrically connected to the metal to be protected. That difference in activity of the two metals induces a current to flow between them, producing corrosion of the more active metal and furnishing cathodic protection to the iron or less active metal.